The problems involved with disposal of discarded automobile tires are receiving increasing attention. Burial of tires within land fills is usually refused because of the unwillingness of tires to remain buried. Because of the size and the flexibility of tires, often a tire buried under five feet of dirt is back at the surface within a decade. For the most part, tires do not rise in elevation but, rather, soil particles fall into cracks and crevasses caused by previous soil settlement. The size of a tire prevents corresponding descent by the tire. Moreover, the resiliency of the tire results in the return of the tire to its normal shape, a process which creates the cracks and crevasses for enhanced settlement of the dirt which surrounds the tire. Thus, increasingly tires are stored in dumps which are fire hazards and breeding grounds for mosquitoes and other insects that flourish within small pockets of trapped water.
Not all used tires are discarded. Tires can be burned to generate electricity. The heat of burning tires is used to drive turbines for the generation of electricity. Nevertheless, the burning of tires for electricity is uncommon, since the profit margin is small.
Material recycling is the answer to the problem of tire disposal. Material recycling, however, raises its own problems. Tires are made of a number of materials and these materials must be separated before recycling can take place. For example, metal bead wires are inserted at the inner diameter of each of a tire's side walls. These bead wires provide the necessary resiliency and support the tire on the wheel of a vehicle. Moreover, the tire is belted, having a material less resilient than rubber along the inner circumference of the tire crown portion. This belting may be metallic, such as steel, or may be fiber.
At one time the rubber salvaged from a used tire was used in making new tires. But the long molecules that give rubber its strength are broken during partial liquefaction in the remolding process, and the resulting tire is unsuitable for the present rugged radial tires. The recycled rubber is used, however, for such purposes as asphalt road resurfacing, and making patches, rubber lining, mats and non-pneumatic wheels. A number of industrial uses also exist. U.S. Pat. Nos. 3,721,392 and 3,658,267 to Burwell teach devices for abrasively removing the rubber from a tire. An endless grinding belt or sander is brought into contact with the tire to provide a pulverized or powdered rubber. However, the properties of the tire material subject the grinding belt or sander to premature wear.
U.S. Pat. Nos. 3,693,894 to Willette and 1,498,935 to Shull teach cutting members, rather than abrasive removal of the rubber. The shape of the tire as it contacts the cutting member in the Willette tire shredder is dictated by the tire itself. Shull, on the other hand, teaches stretching of the tire prior to contact with a cutting member. As a consequence, only a curved portion of the tire is brought into contact with the cutting member, as is to be expected in stripping a curved surface.
It is an object of the present invention to provide an apparatus which recovers rubber from a discarded tire in a useful form and in an efficient manner.